Is the PlayByKey Music Theory MCP server free to use?

Yes. PlayByKey Music Theory is listed on AllMCPs as a free, open Model Context Protocol server you can install into Claude Desktop, Cursor, or any MCP-compatible client.

Is the PlayByKey Music Theory MCP server free to use?

Yes. PlayByKey Music Theory is listed on AllMCPs as a free, open Model Context Protocol server you can install into Claude Desktop, Cursor, or any MCP-compatible client.

PlayByKey Music Theory

Chords, scales, progressions, transposition, and MIDI tools for music theory AI agents.

Quick Install

Automated & IDE Setup

Copy the AI prompt to install this server into Claude Code, Cursor, or another agent — or use 1-click editor setup below.

Add to Cursor Add to VS Code

Manual Client & Custom JSON ConfigExpand JSON ▾

Install Config Generator

Choose your client

claude_desktop_config.json

{
  "mcpServers": {
    "playbykey-music-theory": {
      "command": "npx",
      "args": [
        "-y",
        "playbykey-music-theory"
      ]
    }
  }
}

💡 Paste into ~/Library/Application Support/Claude/claude_desktop_config.json (macOS) or %APPDATA%\Claude\claude_desktop_config.json (Windows)

Documentation Overview

Developer Tools

Packages for PlayByKey - see the table below for what's here.

npm: npmjs.com/package/@playbykey/theory
Documentation: theory-engine.docs.playbykey.com - interactive playgrounds
Changelog: GitHub Releases

Install

Terminal

npm install @playbykey/theory
pnpm add @playbykey/theory
yarn add @playbykey/theory
bun add @playbykey/theory

Quickstart and API examples: packages/theory/README.md

Why @playbykey/theory

Foundation music theory engine: music theory as code. Modes, keys, intervals, and scale relationships resolved deterministically; one source of truth every app, notation tool, or AI agent can build on.
Zero dependencies: no transitive baggage; safe for agents, edge runtimes, and tight bundles
Strictly typed: every function's types exported alongside it, no any
Agent-ready: copy-paste LLM context prompt and interactive docs
Sharps-only notation: one canonical spelling per note (C#, not Db) keeps the Note type safe and unambiguous. Flats are fully supported for both input (parseNote/parseNoteToken accept Db, Eb, Gb, Ab, Bb) and output (getFlats/getEnharmonicLabels), without extending Note itself.

Packages

Package	Description	Links
`@playbykey/theory`	Zero-dependency music theory engine - scales, modes, intervals, chords, progressions, key relationships	npm · docs · changelog
`@playbykey/theory-mcp`	MCP server that exposes the theory engine as AI-callable tools	npm · README
`theory-docs`	Starlight documentation site (private workspace package)	live site · README

License

MIT for the repository tooling and @playbykey/theory. See LICENSE. Individual packages may declare their own license in their package.json.

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Frequently Asked Questions about PlayByKey Music Theory

Add the following block to your claude_desktop_config.json under mcpServers: "mcpServers": { "playbykey-music-theory": { "command": "npx", "args": ["-y", "PlayByKey Music Theory"] } }

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Technical Specs & Signals

CategoryDeveloper Tools

27Quality signal: Emerging · 27/100How this signal is calculated ▾

Server availabilityNot measured

Not scored for repo-hosted servers — we can't reach the running server, only its GitHub page. Hosted MCP endpoints are health-checked live.

Verified ownership8/20

Documentation & tools11/30

Adoption & activity1/15

Community engagement0/10

A guidance signal from public completeness & health data — not a user rating. New listings start lower and rise as they add docs, get verified, and grow adoption. Signals we can't observe for a listing are skipped, not counted against it.

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